This invention relates generally to an air pressure control apparatus, and more particularly to an automatic regulator of air pressure for various storage chambers such as for example freezers, refrigerators, hothouses, drying chambers, or cultivating chambers for various products, which are airtightly constructed and subjected to be heated or cooled.
When storage chambers such as large refrigerators or refrigeration warehouses which have been recently used for a cold storage of various perishable foods are subjected to use at a temperature below -35.degree. C. or a quick freezing, air within the chamber is rapidly cooled at a low temperature, which results in a contraction of air within the chamber, and the chamber is maintained in reduced pressure as compared with the outside. As a consequence, an entrance door of the refrigerator is attracted to the inside of the chamber and the opening of the door is prevented.
When an evaporator of the refrigerator is defrosted with use of electric heater and a temperature within the chamber is significantly raised, air within the chamber is expanded to thereby increase the air pressure abruptly and causes the door to open by breaking a latch or handle of the door. Furthermore, when a temperature change within the chamber is remarkable due to a frequent opening and closing of the door, the opening of the door is prevented or it is unintentionally opened.